Water purification method with nanocomposite sorbent

ABSTRACT

A method for producing a nanocomposite sorbent comprising carbon nanotube-grafted acrylic acid/acrylamide copolymer which involves copolymerization of acrylic acid and acrylamide in the presence of an aqueous dispersion of carbon nanotubes. The method yields a nanocomposite sorbent material having a reversible adsorption capacity phenol of 5 to 2500 μg of phenol per mg of nanocomposite sorbent. Also disclosed is a method for removing organic pollutants from water using the nanocomposite sorbent.

BACKGROUND OF THE INVENTION Field of the Invention

The present disclosure relates to a method of preparing a nanocompositesorbent comprising carbon nanotube-grafted acrylic acid/acrylamidecopolymer composite, the nanocomposite sorbent produced by the method,and a method of removing an organic pollutant from water by adsorptionusing the nanocomposite sorbent.

Discussion of the Background

The “background” description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description which may nototherwise qualify as prior art at the time of filing, are neitherexpressly nor impliedly admitted as prior art against the presentinvention.

Phenol and phenol derivatives have become one of the most prominentpollutants in industrial wastewater. Due to its structure andphysicochemical nature, phenol may disrupt endocrine systems andadversely influence aquatic life as well as human life [L. K. Boateng,J. Heo, J. R. V. Flora, Y. G. Park, Y. Yoon, Sep. Purif. Technol., 116,(2013) 471-478]. Phenols may also block and mimic the activity ofnatural hormones [Y. Park, Z. Sun, G. A. Ayoko, R. L. Frost,Chemosphere, 107, (2014) 249-256].

Phenols, as organic compounds, are widely used in a variety ofindustrial applications, for example as monomers for the synthesis ofpolycarbonates as well as in epoxy resins by the plastics industry.Phenol and phenol derivatives are also used by other industries such aspesticides, paint, steel mill, and petrochemical [J. C. Lazo-Cannata, A.Nieto-Marquez, A. Jacoby, A. L. Paredes-Doig, A. Romero, M. R. Sun-Kou,J. L. Valverde, Sep. Purif. Technol., 80, (2011) 217-224; D. Hank, Z.Azi, S. A. Hocine, O. Chaalal, A. Hellal, J. Ind. Eng. Chem., 20, (2014)2256-2263; and J. Huang, X. Jin, S. Deng, Chem. Eng. J., 192, (2012)192-200]. Phenol is considered one of the major pollutants in wastewaterbecause of its negative impact on the environment. According to theWorld Health Organization (WHO), the maximum allowed level of phenol inpotable water is 1 μg/L [L. Zhu, Y. Deng, J. Zhang, J. Chen, J. ColloidInterfaces Sci., 364, (2011) 462-468 and S. P. Kamble, P. A. Mangrulkar,A. K. Bansiwal, S. S. Rayalu, Chem. Eng. J. 138, (2008) 73-83].

Because of their ubiquitous use in industry and the enormous potentialfor environmental impact, it is essential to mitigate the amount ofphenol that is released during industrial use. [S. Li, Y. Gong, Y. Yang,C. He, L. Hu, L. Zhu, L. Sun, D. Shu, Chem. Eng. J., 260, (2015)231-239]. Thus, there is a need to develop an efficient andcost-effective technology for the effective removal of phenol fromindustrial wastewaters.

Common technologies used to remove phenol include photocatalyticdegradation [A. Shet and S. K. Vidya, Solar Energy, 127, (2016) 67-78],ozonation [H. Biglari, M. Afsharnia, V. Alipour, R. Khosravi, K. Sharafiand A. H. Mahvi, Environmental Science and Pollution Research, 24, 4,(2017) 4105-4116], extraction methods [J. Liu, J. Xie, Z. Ren and W.Zhang, Desalination and Water Treatment, 51, 19-21, (2013) 3826-3831],biological methods [C. Liu, K. Han, D. J. Lee and Q. Wang, Appliedmicrobiology and biotechnology, 100,9, (2016) 4211-4217], membrane-basedseparation [Y. Cui, X. Y. Liu, T. S. Chung, M. Weber, C. Staudt and C.Maletzko, Water research, 91, (2016) 104-114], electrochemical advancedoxidation methods [E. Mousset, L. Frunzo, G. Esposito, E. D vanHullebusch, N. Oturan and M. A. Oturan, Applied Catalysis B:Environmental, 180, (2016) 189-198] and ion exchange [M.D.Victor-Ortega, J. M. Ochando-Pulido and A. Martinez-Ferez, ProcessSafety and Environmental Protection, 100, (2016) 242-251]. These methodshave their drawbacks which include huge costs, partial degradation,non-reusability, and generation of secondary pollutants and toxicsludge. Consequently, adsorption is one of the most appropriatetechniques for the removal of phenol from water due to itsinexpensiveness and effectiveness. Also, the technique produces no toxicwastes. Its performance, however, is highly constrained by materialdesign and properties [S. De Gisi, G. Lofrano, M. Grassi and M.Notarnicola, Sustainable Materials and Technologies, 9, (2016) 10-40].

Carbon-based materials like activated carbon (AC) have beenconventionally been used as adsorbents [A. B. Albadarin, Maurice N.Collins, Mu. Naushad, Saeed Shirazian, Chem. Eng. J., 307, (2017)264-272 and J. Wang and B. Chen, Chemical Engineering Journal, 281,(2015) 379-388]. However, their activity is limited by surface area.Recently, there is a rise in the applications of nano-based materialsfor the adsorption of toxic pollutants [X. Wang, B. Liu, Q. Lu and Q.Qu, Journal of Chromatography A, 1362, (2014) 1-15 and A. A. Alqadami,Mu. Naushad, M. A. Abdalla, T. Ahmad, Z. A. ALOthman, S. M. ALShehri, A.A. Ghfar, J. Cleaner Production, 156, (2017) 426-436]. Amongnanomaterials, the use of graphene for wastewater remediation isbecoming more popular [C. Liu, D. Zhang, L. Zhao, X. Lu, P. Zhang, S.He, G. Hu and X. Tang, RSC Advances, 6, 114, (2016) 113352-113365].Graphene is an allotrope of carbon consisting of a single layer ofcarbon atoms arranged in a hexagonal lattice. It is considered anexcellent adsorbent due to its unique characteristics such as highspecific surface area and ease of synthesis from graphite using anuncomplicated method involving chemical oxidation, exfoliation, andreduction. It has been used for the adsorption of several pollutants,such as dyes [V. K. Gupta, R. Kumar, A. Nayak, T. A. Saleh and M. A.Barakat, Advances in Colloid and Interface Science, 193, (2013) 24-34],toxic ions [T. A. Saleh, A. Sari and M. Tuzen, Chemical EngineeringJournal, 307, (2017) 230-238] and organic contaminants [L. Ji, W. Chen,Z. Xu, S. Zheng and D. Zhu, Journal of environmental quality, 42, 1,(2013) 191-198].

The tendency of graphene and its derivatives to aggregate to reformgraphite and their weak affinity for binding anionic pollutants areconsidered disadvantages to their applications. Nevertheless, thesedisadvantages can be surpassed by covalent or non-covalentfunctionalization with different molecules. This surfacefunctionalization makes graphene and its derivatives more sensitive andselective. Due to the availability of many materials that can be usedfor surface functionalization, the opportunities to study potentialapplications of these materials in the adsorptive treatment ofwastewater are increasing [S. Chowdhury and R. Balasubramanian, Advancesin colloid and interface science, 204, (2014) 35-56]. So far, a numberof functionalized graphene, graphene oxide, and reduced graphene oxidehave been successfully synthesized and extensively investigated asadsorbents for water purification. Materials used for functionalizationof carbon nanostructures include organic polymers and nanosized metaloxide [B. Bolto and J. Gregory, Water research, 41, 11, (2007) 2301-2324and R. K. Upadhyay, N. Soin and S. S. Roy, Rsc Advances, 4, 8, (2014)3823-3851]. These materials can be grafted on the surface without anyrequirement of crosslinkers which usually reduce the binding sites forpollutants. Carbon nanotubes (CNTs) have been extensively used in manyfields, including efficacious adsorbents for removal of contaminants [XuJ., Sheng T., Hu Y., Baig S. A., Lv X. and Xu X., Chem. Eng. J., 219,(2013) 162-173]. CNTs can adsorb organic contaminants because of theirstrong affinities [Mashallah Rezakazemi, Tonni Agustiono Kurniawan,Ahmad B. Albadarin, Saeed Shirazian, Journal of Molecular Liquids, 271,(2018) 24-30]. It was reported that the phenol removal mechanism in CNTis a combination of physical trapping and lateral surface adsorption.Grafting of CNT with polymeric branches could enhance the adsorption ofphenol by introducing more active sites for trapping the phenol.

In view of the forgoing, one object of the present disclosure is toprovide a method for producing a new nanocomposite sorbent materialusing carbon nanotubes and a copolymer of acrylic acid and acrylamide,which provides reduced aggregation and that may be advantageous forwater purification in comparison to conventional materials. Anotherobject of the present disclosure is to provide nanocomposite sorbentshaving increased adsorption capacities for phenol and other organicpollutants that may be conveniently reused and do not create toxicbyproducts.

SUMMARY OF THE INVENTION

The present disclosure relates to a method of preparing a nanocompositesorbent comprising carbon nanotube-grafted acrylic acid/acrylamidecopolymer composite involving mixing an aqueous suspension of carbonnanotubes with acrylic acid and acrylamide to form a dispersion, addinga polymerization initiator to form a reaction mixture, heating thereaction mixture to a temperature of 25 to 100° C., and isolating thenanocomposite sorbent, wherein a weight ratio of acrylic acid toacrylamide in the reaction mixture is 0.75:1 to 1.25:1.

In preferred embodiments, the carbon nanotubes are present in thenanocomposite sorbent in an amount of 0.01 to 2 wt % based on a totalweight of the nanocomposite sorbent.

In some embodiments, the carbon nanotubes have a length of 50 to 125 μmand an average diameter of 5 to 7 nm.

In some embodiments, the carbon nanotubes are prepared by a chemicalvapor deposition method using ethylene at a temperature of 800 to 1100°C.

In some embodiments, the mixing comprises adding acrylamide to asuspension of carbon nanotubes then adding acrylic acid.

In preferred embodiments, the polymerization initiator is an alkalimetal persulfate salt.

In preferred embodiments, the nanocomposite sorbent comprises 70 to 80wt % carbon, 5 to 10 wt % nitrogen, and 10 to 25 wt % oxygen, based on atotal weight of non-hydrogen elements of the nanocomposite sorbent.

In some embodiments, the nanocomposite sorbent has a phenol adsorptioncapacity of 5 to 2500 μg of phenol per mg of nanocomposite.

The present disclosure also relates to a nanocomposite sorbentcomprising carbon nanotube-grafted acrylic acid/acrylamide copolymercomposite, wherein carbon nanotube-grafted acrylic acid/acrylamidecopolymer composite comprises 37.5 to 62.5 wt % of poly(acrylic acid),0.01 to 2 wt % of carbon nanotubes, and the remaining wt % ofpolyacrylamide, each based on a total weight of the carbonnanotube-grafted acrylic acid/acrylamide copolymer composite, wherein aweight ratio of poly(acrylic acid) to polyacrylamide in the carbonnanotube-grafted acrylic acid/acrylamide copolymer composite is 0.75:1to 1.25:1.

In preferred embodiments, the nanocomposite sorbent comprises 70 to 80wt % carbon, 5 to 10 wt % nitrogen, and 10 to 25 wt % oxygen, each basedon a total weight of non-hydrogen elements of the nanocomposite sorbent.

In some embodiments, the carbon nanotubes have a length of 50 to 125 μmand an average diameter of 5 to 7 nm.

In preferred embodiments, the nanocomposite sorbent has a reversiblephenol adsorption capacity of 5 to 2500 μg of phenol per mg ofnanocomposite sorbent.

In preferred embodiments, the nanocomposite retains 90 to 100% of thereversible phenol adsorption capacity after 6 cycles ofadsorption-elution.

The current disclosure also relates to a method for removing an organicpollutant from water comprising contacting water containing the organicpollutant with the nanocomposite sorbent.

In some embodiments, the nanocomposite sorbent is employed in an amountof 0.2 to 20 mg per mL of the water.

In some embodiments, the method further comprises eluting the organicpollutant from the nanocomposite sorbent by washing with a wash solvent.

In some embodiments, the water has a pH of 6.5 to 14 and thenanocomposite sorbent is contacted with the water for 5 to 120 minutes.

In some embodiments, the organic pollutant is a phenol.

In preferred embodiments, the nanocomposite sorbent has a reversiblephenol adsorption capacity of 5 to 2500 μg of phenol per mg ofnanocomposite sorbent.

In preferred embodiments, the nanocomposite sorbent retains 90 to 100%of the reversible phenol adsorption capacity after 6 cycles ofadsorption-elution.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 shows a schematic depiction of the CNT chemical vapor depositionsynthesis system;

FIG. 2A is a transmission electron microscopy (TEM) image of thesynthesized CNTs;

FIG. 2B is a scanning electron microscopy (SEM) image of the synthesizedCNTs on a growth substrate;

FIG. 3 shows an illustration of the structure of the nanocompositesorbent comprising carbon nanotube-grafted acrylic acid/acrylamidecopolymer composite;

FIG. 4 shows the powder X-ray diffraction pattern of the as-synthesizedCNTs;

FIG. 5 shows the Fourier transform infrared (FTIR) spectrum of theas-synthesized CNTs and the nanocomposite sorbent;

FIG. 6A is a low-magnification SEM image (×330) of the nanocompositesorbent;

FIG. 6B is a high-magnification SEM image (×10,000) of the nanocompositesorbent;

FIG. 7 shows the EDX spectrum of the nanocomposite sorbent;

FIGS. 8A-8C show the factorial design plots of phenol adsorption overthe nanocomposite sorbent, where FIG. 8A shows the normal plot of thestandardized effects, FIG. 8B shows the main effects plots of response,and FIG. 8C shows the Pareto Chart of the standardized effect

FIG. 9 shows the interaction plots for the response of data means forthe adsorption of phenol over the nanocomposite sorbent;

FIG. 10 shows the recycling performance of the nanocomposite sorbent forthe adsorption and desorption of phenol over the nanocomposite sorbent;and

FIG. 11 shows a depiction of the physisorption interactions betweenphenol and the nanocomposite sorbent.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, it is understood that other embodimentsmay be utilized and structural and operational changes may be madewithout departure from the scope of the present embodiments disclosedherein.

Definitions

The phrase “substantially free”, unless otherwise specified, describes aparticular component being present in an amount of less than about 1 wt.%, preferably less than about 0.5 wt. %, more preferably less than about0.1 wt. %, even more preferably less than about 0.05 wt. %, yet evenmore preferably 0 wt. %, relative to a total weight of the compositionbeing discussed.

As used herein, the terms “optional” or “optionally” means that thesubsequently described event(s) can or cannot occur or the subsequentlydescribed component(s) may or may not be present (e.g., 0 wt. %).

As used herein, “adsorption” is the adhesion of atoms, ions or moleculesfrom a gas, liquid, or dissolved solid to a surface. The process createsa film of an adsorbate (e.g. the first gas) on the surface of anadsorbent (e.g. the fluorinated carbon adsorbent). Chemisorption is akind of adsorption which involves a chemical reaction between theadsorbate and adsorbent, i.e., new chemical bonds are generated at theadsorbent surface. In contrast with chemisorption is physisorption,which leaves the chemical species of the adsorbate and adsorbent intactchemically unchanged upon adsorption.

Method for Preparing Nanocomposite Sorbent

According to a first aspect, the present disclosure relates to a methodof making a nanocomposite sorbent. Generally, the method involvespolymerizing acrylic acid and acrylamide in the presence of a suspensionof carbon nanotubes at 25 to 100° C.

Carbon nanotubes can be classified by features such as their electricalproperties, number of walls, the geometric configuration of the atomsthat make up the nanotube. Classified by their electronic properties,carbon nanotubes can be either metallic or semiconducting. In thiscontext, “metallic” means having no band gap and displaying conductivitysimilar to that of a metal, i.e. with a Fermi level lying in theconduction band of the material and a conductivity which decreases astemperature increases. In this context, “semiconducting” means having aband gap, a Fermi level lying in the band gap, and a conductivity thatincreases as temperature increases. Classified by their number of walls,carbon nanotubes can be single-walled carbon nanotubes (SWCNT) whichhave only one layer of carbon atoms arranged into a tube with an edgering of carbon atoms, or multi-walled carbon nanotubes (MWCNT), whichhave more than one single-layer tube of carbon atoms arranged so as tobe nested, one tube inside another, each tube sharing a commonorientation. Closely related to MWNTs are carbon nanoscrolls. Carbonnanoscrolls are structures similar in shape to a MWCNT, but made of asingle layer of carbon atoms that has been rolled onto itself to form amulti-layered tube with a free outer edge on the exterior of thenanoscroll and a free inner edge on the interior of the scroll and openends. The end-on view of a carbon nanoscroll has a spiral-like shape.For the purposes of this disclosure, carbon nanoscrolls are considered atype of MWCNT. Classified by the geometric configuration of the atomsthat make up the nanotube, carbon nanotubes can be described by a pairof integer indicies n and m. The indicies n and m denote the number ofunit vectors along two directions in the honeycomb crystal lattice of asingle layer of carbon atoms. If m=0, the nanotubes are called zigzagtype nanotubes. If n=m, the nanotubes are called armchair typenanotubes. Otherwise they are called chiral type nanotubes. In someembodiments, the carbon nanotubes are metallic. In other embodiments,the carbon nanotubes are semiconducting. In some embodiments, the carbonnanotubes are SWCNTs. In other embodiments, the carbon nanotubes areMWCNTs. In some embodiments, the carbon nanotubes are carbonnanoscrolls. In some embodiments, the carbon nanotubes are zigzag typenanotubes. In alternative embodiments, the carbon nanotubes are armchairtype nanotubes. In other embodiments, the carbon nanotubes are chiraltype nanotubes.

Carbon nanotubes may further be described by the functionalization ofthe carbon nanotubes after synthesis. Examples of functionalizationtypes that carbon nanotubes may be subjected to include covalentmodification and non-covalent modification. Examples of covalentmodifications include oxidation, esterification, amidation,halogenation, cycloaddition, radical addition, nucleophilic addition, orelectrophilic addition. Examples of non-covalent modifications includeassociation of aromatic or other molecules containing a π-electronsystem, or wrapping or encasement in polymeric or dendrimeric materialssuch as proteins, polymers, polysaccharides, phospholipids, or the like.Carbon nanotubes that have not undergone a functionalization procedureafter synthesis are known as “pristine carbon nanotubes”.

In preferred embodiments, the carbon nanotubes are pristine carbonnanotubes. In preferred embodiments, the carbon nanotubes are connecteddirectly to a main carbon chain of an acrylic acid/acrylamide copolymer.In preferred embodiments, the connection between the carbon nanotubesand the main carbon chain of the acrylic acid/acrylamide copolymer is acovalent bond. In preferred embodiments, the aforementioned covalentbond is a carbon-carbon bond. In preferred embodiments, theaforementioned carbon-carbon bond includes a carbon that is either inthe tube or on the edge ring of the carbon nanotube.

In preferred embodiments, the carbon nanotubes have an average length of50 to 125 μm, preferably 55 to 120 μm, preferably 60 to 115 μm,preferably 65 to 110 μm, preferably 70 to 105 μm, preferably 75 to 100μm, preferably 80 to 95 μm, preferably 85 to 90 μm. In preferredembodiments, the carbon nanotubes have an average diameter of 5 to 7 nm,preferably 5.1 to 6.9 nm, preferably 5.2 to 6.8 nm, preferably 5.3 to6.7 nm, preferably 5.5 to 6.6 nm, preferably 5.6 to 6.5 nm, preferably5.7 to 6.4 nm, preferably 5.8 to 6.3 nm, preferably 5.9 to 6.2 nm,preferably 6.0 to 6.1 nm.

Carbon nanotubes are typically made using methods including arcdischarge, laser ablation, thermal plasma or plasma torch synthesis,chemical vapor deposition (CVD), liquid electrolysis, and controlledflame synthesis. The arc discharge method involves an arc dischargebetween electrodes, one or more of which are graphite. Laser ablationinvolves the irradiation of a graphite target with a pulsed laser athigh temperature in an inert atmosphere.

Plasma torch synthesis (also known as thermal plasma method) involvesthe use of a torch capable of producing jet or directed flow of plasmafrom a gas and an electrical discharge arc. It differs from the arcdischarge method in that the carbon used to make the carbon nanotubes isin the plasma torch synthesis is derived from a carbon-containing gas,not vaporized graphite like in the arc discharge method. Liquidelectrolysis involves electrolytic treatment of molten carbonate saltssuch as lithium carbonate. Controlled flame synthesis involves the useof natural flames from combustion of carbon-containing material.Chemical vapor deposition (CVD) involves the catalytic decomposition ofa carbon-containing gas on a substrate at elevated temperature. In someembodiments, the carbon nanotubes are made by an arc discharge method, alaser ablation method, a thermal plasma or plasma torch synthesismethod, a liquid electrolysis method, or a controlled flame synthesismethod. In preferred embodiments, the carbon nanotubes are made using aCVD method. In preferred embodiments, the CVD method used to make thecarbon nanotubes uses ethylene as the carbon-containing gas. Inpreferred embodiments, the CVD method used to make the carbon nanotubesis performed at 800 to 1100° C., preferably 820 to 1020° C. In preferredembodiments, the CVD method used to make the carbon nanotubes involvespre-heating the ethylene gas to 900 to 1100° C., preferably 950 to 1050°C., preferably 1000 to 1030° C., preferably to 1020° C. In preferredembodiments, the CVD method used to make the carbon nanotubes involves agrowth chamber where the decomposition of the ethylene gas takes placethat is kept at a temperature of 800 to 900° C., preferably 810 to 850°C., preferably 820° C.

In some embodiments, the carbon nanotubes are mixed with acrylamide andacrylic acid. In preferred embodiments, the carbon nanotubes aredispersed in water to form an aqueous suspension of carbon nanotubesthat is mixed with acrylamide and acrylic acid. In preferredembodiments, the aqueous dispersion of carbon nanotubes is mixed withacrylamide to form an acrylamide-CNT dispersion, then acrylic acid isadded to the acrylamide-CNT dispersion.

Following the mixing, a polymerization initiator is added to form areaction mixture. In preferred embodiments, the polymerization initiatoris an alkali metal or ammonium persulfate salt. In some embodiments, thepolymerization initiator and/or dispersion are heated before theaddition. In preferred embodiments, the polymerization initiator and/ordispersion are heated to a temperature of 40 to 60° C., preferably 45 to55° C., preferably 50° C. In preferred embodiments, the polymerizationinitiator is added while the dispersion is at a temperature of 40 to 60°C., preferably 45 to 55° C., preferably 50° C. In preferred embodiments,the polymerization initiator is an alkali metal persulfate salt. In someembodiments, the polymerization initiator is potassium persulfate. Inpreferred embodiments, the weight ratio of the polymerization initiatorto the acrylic acid present in the reaction mixture is 0.00001 to 0.1,preferably 0.00005 to 0.05, preferably 0.0001 to 0.01, preferably 0.0005to 0.005, preferably 0.001. In preferred embodiments, the weight ratioof the acrylic acid to acrylamide in the reaction mixture is 0.75:1to 1. 25:1, preferably 0.8:1 to 1.2:1, preferably 0.85:1 to 1. 15:1,preferably 0.9:1 to 1.1:1, preferably 0.95:1 to 1.05:1, preferably 1:1.In preferred embodiments, the weight ratio of the CNTs to the acrylicacid present in the reaction mixture is 0.00001 to 0.1, preferably0.00005 to 0.05, preferably 0.0001 to 0.01, preferably 0.0005 to 0.005,preferably 0.001. Following the addition of the polymerizationinitiator, the reaction mixture is heated while stirring to afford thenanocomposite. In preferred embodiments, the reaction mixture is heatedto 25 to 100° C., preferably 30 to 90° C., preferably 35 to 80° C.,preferably 40 to 70° C., preferably 45 to 60° C., preferably 50° C. Insome embodiments, the reaction mixture is heated while stirring for 0.5to 48 hours, preferably 1 to 24 hours, preferably 2 to 20 hours,preferably 3 to 18 hours, preferably 4 to 16 hours. This step may bereferred to as a “polymerization step”.

Following the polymerization step, the nanocomposite may be collected byany solid-liquid separation technique known to those of ordinary skillin the art, for example, filtration, decantation, centrifugation, or thelike, but excluding techniques such as evaporation. In preferredembodiments, the collected nanocomposite is dried. In some embodiments,the nanocomposite is dried at 30 to 130° C., preferably 40 to 120° C.,preferably 50 to 110° C., preferably 60 to 100° C., preferably 70 to 90°C., preferably 75 to 85° C., preferably 80° C., preferably 95 to 105°C., preferably 100° C. for 1 to 72 hours, preferably 6 to 66 hours,preferably 12 to 60 hours, preferably 18 to 54 hours, preferably 24 to50 hours, preferably 36 to 49 hours, preferably 48 hours. In someembodiments the nanocomposite may be reduced to a powder of smallparticles. In some embodiments, the nanocomposite may be reduced to apowder of small particles by a technique such as milling, grinding, ballmilling, chopping, pulverizing, crushing, pounding, mincing, shredding,smashing, fragmenting, or another technique that may be used to reduce amaterial to smaller particles. In some embodiments, the technique maytake place using a mill, ball mill, rod mill, autogenous mill,semi-autogenous grinding mill, pebble mill, buhrstone mill, burr mill,tower mill, vertical shaft impactor mill, grinder, pulverizer, mortarand pestle, blender, crusher, or other implement used to reduce amaterial to smaller particles. In preferred embodiments, thenanocomposite is reduced to a powder of particles with a size of 0.001to 1000 μm, preferably 0.005 to 500 μm, preferably 0.01 to 100 μm,preferably 0.05 to 50 μm, preferably 0.075 to 25 μm, preferably 0.1 to10 μm, preferably 0.25 to 7. 5 μm, preferably 0.5 to 5μm, preferably 0.6to 4 μm. In preferred embodiments, nanocomposite is washed with a washsolvent to remove any impurities before the drying step. In preferredembodiments, the wash solvent is deionized water. In preferredembodiments, the nanocomposite is washed repeatedly until the washingshave so visible sign of particulate matter, cloudiness, or color.

Nanocomposite Sorbent Comprising Carbon Nanotube Grafted AcrylicAcid/Acrylamide Copolymer Composite

A second aspect of the disclosure relates to a nanocomposite sorbentcomprising carbon nanotube grafted acrylic acid/acrylamide copolymercomposite. In preferred embodiments, the nanocomposite sorbent has acarbon content of 70 to 80 wt %, preferably 71 to 79 wt %, preferably 72to 77 wt %, preferably 73 to 75 wt %, a nitrogen content of 5 to 10 wt%, preferably 6 to 9.5 wt %, preferably 7 to 9 wt %, and an oxygencontent of 10 to 25 wt %, preferably 12 to 24 wt %, preferably 13 to 22wt %, preferably 15 to 20 wt %, preferably 17 to 19 wt %, each based onthe total weight of the non-hydrogen elements of the nanocompositesorbent. In preferred embodiments, the nanocomposite sorbent has apoly(acrylic acid) content of 37. 5 to 62. 5 wt %, preferably 40 to 60wt %, preferably 42. 5 to 57. 5 wt %, preferably 45 to 55 wt %,preferably 47.5 to 50 wt %, preferably 48 to 49. 95 wt %, and a carbonnanotube content of 0.001 to 2 wt %, preferably 0.005 to 1 wt %,preferably 0.01 to 0.1 wt %, preferably 0.05 wt %, and a polyacrylamidecontent of the remaining wt % of the nanocomposite sorbent, each basedon the total weight of the nanocomposite sorbent. In preferredembodiments, the weight ratio of poly(acrylic acid) to polyacrylamide inthe nanocomposite sorbent is 0.75:1 to 1.25:1, preferably 0.8:1 to1.2:1, preferably 0.85:1 to 1.15:1, preferably 0.9:1 to 1.1:1,preferably 0.95:1 to 1.05:1, preferably 1:1.

In some embodiments, the nanocomposite sorbent is capable of adsorbingorganic pollutants. In preferred embodiments, the nanocomposite sorbentis capable of adsorbing phenol. In preferred embodiments, thenanocomposite sorbent has a phenol adsorption capacity of 5 to 2500 μg,preferably 10 to 1000 μg, preferably 25 to 500 μg, preferably 50 to 250μg of phenol per mg of nanocomposite sorbent.

In preferred embodiments, the adsorbed organic pollutants are adsorbedto the nanocomposite sorbent through interaction with the carbonnanotube, the acrylic acid/acrylamide copolymer, or both. In someembodiments, the interaction between the organic pollutant and thecarbon nanotube are π-π interactions or electrostatic interaction orboth. In some embodiments, the interaction of the organic pollutant andthe acrylic acid/acrylamide copolymer are π-π interactions or hydrogenbonding or both.

In some embodiments, adsorbed organic pollutants can be eluted from thenanocomposite sorbent. In some embodiments, adsorbed organic pollutantscan be eluted by washing with a wash solvent. In some embodiments, thewash solvent comprises an organic solvent. Examples of organic solventsinclude acetone, isopropanol, ethanol, methanol, butanol, ethyl acetate,tetrahydrofuran, methyl ethyl ketone, dimethylformamide, benzene,toluene, xylene, chloroform, dichloromethane, propylene carbonate,ethylene glycol, glycerol and mixtures thereof. In preferredembodiments, the wash solvent is an alcoholic solvent such as methanol,ethanol, propanol, butanol, and the like. In preferred embodiments, thenanocomposite sorbent retains 90 to 100%, preferably 91 to 99.9%,preferably 92 to 99.8%, preferably 93 to 99.7%, preferably 94 to 99.6%,preferably 95 to 99.5% of the phenol adsorption capacity after 6 cyclesof adsorption-elution.

In some embodiments, the nanocomposite sorbent is comprised of particleshaving a mean particle size of 0.01 μm to 10 cm, preferably 0.1 μm to 5cm, preferably 1μm to 1 cm, preferably 10 to 500 μm. The particles mayhave a spherical shape, or may be shaped like cylinders, boxes, blocks,spikes, flakes, plates, ellipsoids, toroids, stars, ribbons, discs,rods, granules, prisms, cones, platelets, sheets, angular chunks, orsome other shape. In one embodiment, the nanocomposite sorbent may be inthe form of agglomerates. As used herein, the term “agglomerates” refersto a clustered particulate composition comprising primary particles, theprimary particles being aggregated together in such a way so as to formclusters thereof, at least 50 volume percent of the clusters having amean diameter that is at least 2 times the mean diameter of the primaryparticles, and preferably at least 90 volume percent of the clustershaving a mean diameter that is at least 5 times the mean diameter of theprimary particles. The primary particles may be the particles ofnanocomposite sorbent having a mean diameter as previously described. Insome embodiments, the surface of the particles or agglomerates of thenanocomposite sorbent are irregular and non-smooth. In some embodiments,the surface of the nanocomposite sorbent have or comprise an irregulararrangement of fibers made of a copolymer or carbon nanotubes. In someembodiments, the irregular arrangement of fibers made of a copolymer orcarbon nanotubes contains fibers that are randomly arranged, coiled,interwoven, overlapping, or otherwise tangled. In some embodiments, theirregular arrangement of fibers has the appearance of a web, net, knot,tangle, or other ordered or disordered arrangement of fibers.

Method for Removing an Organic Pollutant from Water

A third aspect of the disclosure relates to a method for removing anorganic pollutant from water using the nanocomposite sorbent describedabove. In some embodiments, only one organic pollutant is present in thewater. In alternative embodiments, a plurality of organic pollutants ispresent in the water. The method involves contacting the nanocompositesorbent with water containing one or more organic pollutants.

In some embodiments, the organic pollutants may be a dye, a phenol, apolycyclic aromatic hydrocarbon, an herbicide, a pesticide, a persistentorganic pollutant, or the like, preferably the organic pollutant is aphenol.

In some embodiments, the organic pollutant is a dye. A dye is a coloredsubstance that chemically binds to a material it may be intended tocolor. Generally, a dye is applied in solution, typically aqueoussolution. Examples of dyes include, but are not limited to: acridinedyes, which are acridine and its derivatives such as acridine orange,acridine yellow, acriflavine, and gelgreen; anthraquinone dyes, whichare anthroaquinone and its derivatives such as acid blue 25, alizarin,anthrapurpurin, carminic acid, 1,4-diamno-2,3-dihydroanthraquinone,7,14-dibenzypyrenequinone, dibromoanthrone, 1,3-dihydroxyanthraquinone,1,4-dihydroxyanthraquinone, disperse red 9, disperse red 11, indanthroneblue, morindone, oil blue 35, parietin, quinizarine green SS, remazolbrilliant blue R, solvent violet 13, 1,2,4-trihydroxyanthraquinone, vatorange 1, and vat yellow 1; diaryl methane dyes such as auramine 0,triarylmethane dyes such as acid fuchsin, aluminon, aniline blue WS,aurin, aurintricarboxylic acid, brilliant blue FCF, brilliant green,bromocresol green, bromocresol purple, bromocresol blue, bromophenolblue, bromopyrogallol red, chlorophenol red, coomassie brilliant blue,cresol red, O-cresolphthalein, crystal violet, dichlorofluorescein,ethyl green, fast green FCT, FIAsH-EDT2, fluoran, fuchsine, green S,light green SF, malachite green, merbromin, metacresol purple, methylblue, methyl violet, naphtholphthalein, new fuchsine, pararosaniline,patent blue V, phenol red, phenolphthalein, phthalein dye, pittacal,spirit blue, thymol blue, thymolphthalein, Victoria blue BO, Victoriablue R, water blue, xylene cyanol, and xylenol orange; azo dyes such asacid orange 5, acid red 13, alican yellow, alizarine yellow R, allurared AC, amaranth, amido black 10B, aniline yellow, arylide yellow, azoviolet, azorubine, basic red 18, biebrich scarlet, Bismarck brown Y,black 7984, brilliant black BN, brown FK, chrysoine resorcinol, citrusred 2, congo red, D&C red 33, direct blue 1, disperse orange 1,eriochrome black T, evans blue, fast yellow AB, orange 1,hydroxynaphthol blue, janus green B, lithol rubine BK, metanil yellow,methyl orange, methyl red, methyl yellow, mordant brown 33, mordant red19, naphthol AS, oil red 0, oil yellow DE, orange B, orange G, orangeGGN, para red, pigment yellow 10, ponceau 2R, prontosil, red 2G, scarletGN, Sirius red, solvent red 26, solvent yellow 124, sudan black B, sudanI, sudan red 7B, sudan stain, tartrazine, tropaeolin, trypan blue, andyellow 2G; phthalocyanine dyes such as phthalocyanine blue BN,phthalocyanine Green G, Alcian blue, and naphthalocyanine , azin dyessuch as basic black 2, mauveine, neutral red, Perkin's mauve, phenazine,and safranin; indophenol dyes such as indophenol anddichlorophenolindophenol; oxazin dyes; oxazone dyes; thiazine dyes suchas azure A, methylene blue, methylene green, new methylene blue, andtoluidine blue; thiazole dyes such as primuline, stains-all, andthioflavin; xanthene dyes such as 6-carboxyfluorescein, eosin B, eosinY, erythosine, fluorescein, rhodamine B, rose bengal, and Texas red;fluorone dyes such as calcein, carboxyfluorescein diacetate succinimidylester, fluo-3, fluo-4, indian yellow, merbromin, pacific blue, phloxine,and seminaphtharhodafluor; or rhodamine dyes such as rhodamine,rhodamine 6G, rhodamine 123, rhodamine B, sulforhodamine 101, andsulforhodamine B.

A phenol is an organic compound consisting of a hydroxyl group (—OH)bonded directly to an aromatic hydrocarbon group. Examples of phenolsinclude, but are not limited to, phenol (the namesake of the group ofcompounds), bisphenols (including bisphenol A), butylated hydroxytoluene(BHT), 4-nonylphenol, orthophenyl phenol, picric acid, phenolphthaleinand its derivatives mentioned above, xylenol, diethylstilbestrol,L-DOPA, propofol, butylated hydroxyanisole, 4-tert-butylcatechol,tert-butylhydroquinone, carvacrol, chloroxyleol, cresol (including M-,O-, and P-cresol), 2,6-di-tert-butylphenol,2,4-dimethyl-6-tert-butylphenol, 2-ethyl-4,5-dimethylphenol,4-ethylguaiacol, 3-ethylphenol, 4-ethylphenol, flexirubin, mesitol,1-nonyl-4-phenol, thymol, 2,4,6-tri-tert-butylphenol, chlorophenol(including 2-, 3-, and 4-chlorophenol), dichlorophenol (including 2,4-and 2,6-dichlorophenol), bromophenol, dibromophenol (including2,4-dibromophenol), nitrophenol, norstictic acid, oxybenzone, andparacetamol (also known as acetoaminophen).

A polycyclic aromatic hydrocarbon (PAH) is an aromatic hydrocarboncomposed of multiple aromatic rings. Examples of polycyclic aromatichydrocarbons include naphthalene, anthracene, phenanthrene, phenalene,tetracene, chrysene, triphenylene, pyrene, pentacene, benzo[a]pyrene,corannulene, benzo[g,h,i]perylene, coronene, ovalene, benzo[c]fluorine,acenaphthene, acenaphthylene, benz[a]anthracene, benzo[b]fluoranthene,benzo[j]fluoranthene, benzo[k]fluoranthene, benzo[e]pyrene,cyclopenta[c,d]pyrene, dibenz[a,h]anthracene, dibenzo[a,e]pyrene,dibenzo[a,h]pyrene, dibenzo[a,i]pyrene, dibenzo[a,l]pyrene,fluoranthene, fluorine, indeno[1,2,3-c,d]pyrene, 5-methylchrysene,naphthacene, pentaphene, picene, and biphenylene.

An herbicide (also known as “weedkiller”) is a substance that is toxicto plants and may kill, inhibit the growth of, or prevent thegermination of plants. Herbicides are typically used to control thegrowth of or remove unwanted plants from an area of land, particularlyin an agricultural context. Examples of herbicides include, but are notlimited to, 2,4-D, aminopyralid, chlorsulfuron, clopyralid, dicamba,diuron, glyphosate, hexazinone, imazapic, imazapyr, methsulfuron methyl,picloram, sulfometuron methyl, triclopyr, fenoxaprop, fluazifop,quizalofop, clethodim, sethoxydim, chlorimuron, foramsulfuron,halosulfuron, nicosulfuron, primisulfuron, prosulfuron, rimsulfuron,thofensulfuron, tribenuron, imazamox, imazaquin, flumetsulam,cloransulam, thiencarbazone, fluoxpyr, diflufenzopyr, atrazine,simazine, metribuzin, bromoxynil, bentazon, linuron, glufosinate,clomazone, isoxaflutole, topramezone, mesotrione, tembotrione,acifluorfen, formesafen, lactofen, flumiclorac, flumioxazin,fulfentrazone, carfentrazone, fluthiacet-ethyl, falufenacil, paraquat,ethalfluralin, pendimethalin, trifluralin, butylate, EPTC,ecetochlor,alachlor, metolachlor, dimethenamid, flufenacet, andpyroxasulfone.

A pesticide is a substance meant to prevent, destroy, or control pestsincluding, but not limited to algae, bacteria, fungi, plants, insects,mites, snails, rodents, and viruses.

A pesticide intended for use against algae is known as an algicide.Examples of algicides include benzalkonium chloride, bethoxazin,cybutryne, dichlone, dichlorophen, diuron, endothal, fentin,isoproturon, methabenthiazuron, nabam, oxyfluorfen, pentachlorophenyllaurate, quinoclamine, quinonamid, simazine, terbutryn, and tiodonium.

A pesticide intended for use against bacteria is known as a bactericide.Examples of bactericides include antibiotics such as: aminoglycosidessuch as amikacin, gentamicin, kanamycin, neomycin, netilmicin,tobramycin, paromomycin, streptomycin, and spectinomycin; ansamycinssuch as geldanamycin, herbimycin, and rifaximin; carbacephems such asloracarbef; carbapenems such as ertapenem, doripenem, imipenem, andmeropenem; cephalosporins such as cefadroxil, cefazolin, cephradine,cephapirin, cephalothin, cephalexin, cefaclor, cefoxitin, cefotetan,cefamandole, cefmetazole, cefonicid, cefprozil, cefuroxime, cefixime,cefdinir, cefditoren, cefoperazone, cefotaxime, cefpodoxime, cefazidime,ceftibuten, ceftizoxime, moxalactam, ceftriaxone, cefepime, cefarolinefosamil, and ceftobiprole; glycopeptides such as teicoplanin,vancomycin, telavancin, dalbavancin, and oritavancin; lincosamides suchas clindamycin and lincomycin; lipopeptides such as daptomycin;macrolides such as azithromycin, clarithromycin, erythromycin,roxithromycin, telithromycin, spiramycin, and fidoxamicin; monobactamssuch as aztreonam; nitrofurans such as furazolidone and nitrofurantoin;oxazolidinones such as linezolid, posizolid, radezolid, and torezolid;penicillins such as amoxicillin, ampicillin, azlocillin, dicloxacillin,flucloxacillin, mezlocillin, methicillin, nafcillin, oxacillin,penicillins (including penicillin G and V), piperacillin, temocillin,and ticarcillin; polypeptides such as bacitracin, colistin, andpolymyxin B; quinolones such as ciproflaxacin, enoxacin, gatifloxacin,gemifloxacin, levofloxacin, lomefloxacin, moxifloxacin, nadifloxacin,nalidixic acid, norfloxacin, ofloxacin, trovafloxacin, gepafloxacin,sparfloxacin, and temafloxacin; sulfonamides such as mafenide,sulfacetamide, sulfadiazine, sulfadithoxine, sulfamethizole,sulfamethoxazole, sulfanilamide, sulfasalazine, sulfisoxazole, andsulfonamidochrysoidine; tetracyclines such as demeclocycline,doxycycline, metacycline, minocycline, oxytetracycline, andtetracycline.

A pesticide intended for use against fungi is known as a fungicide.Examples of fungicides include acibenzolar, acypetacs, aldimorph,anilazine, aureofungin, azaconazole, azithiram, azoxystrobin, benalaxyl,benodanil, benomyl, benquinox, benthiavalicarb, binapacryl, biphenyl,bitertanol, bixafen, blasticidin-S, boscalid, bromuconazole, captafol,captan, carbendazim, carboxin, carpropamid, chloroneb, chlorothalonil,chlozolinate, cyazofamid, cymoxanil, cyprodinil, dichlofluanid,diclocymet, dicloran, diethofencarb, difenoconazole, diflumetorim,dimethachlone, dimethomorph, diniconazole, dinocap, dodemorph,edifenphos, enoxastrobin, epoxiconazole, etaconazole, ethaboxam,ethirimol, etridiazole, famoxadone, fenamidone, fenarimol,fenbuconazole, fenfuram, fenhexamid, fenoxanil, fenpropidin,fenpropimorph, ferbam, fluazinam, fludioxonil, flumorph, fluopicolide,fluopyram, fluoroimide, fluoxastrobin, flusilazole, flutianil,flutolain, flopet, fthalide, furalaxyl, guazatine, hexaconazole,hymexazole, imazalil, imibenconazole, iminoctadine, iodocarb,ipconazole, iprobenfos, iprodione, iprovalicarb, siofetamid,isoprothiolane, isotianil, kasugamycin, laminarin, mancozeb,mandestrobin, mandipropamid, maneb, mepanypyrim, mepronil,meptyldinocap, mealaxyl, metominostrobin, metconazole, methafulfocarb,metiram, metrafenone, myclobutanil, naftifine, nuarimol, octhilinone,ofurace, orysastrobin, oxadixyl, oxathiapiprolin, oxolinic acid,oxpoconazole, oxycarboxin, oxytetracycline, pefurazate, penconazole,pencycuron, penflufen, penthiopyrad, phenamacril, picarbutrazox,picoxystrobin, piperalin, polyoxin, probenzole, prochloraz, procymidone,propamocarb, propiconazole, propineb, proquinazid, prothiocarb,prothioconazole, pydiflumetofen, pyraclostrobin, pyrametostrobin,pyraoxystrobin, pyrazophos, pyribencarb, pyributicarb, pyrifenox,pyrimethanil, pyrimorph, pyriofenone, pyroquilon, quinoxyfen,quintozene, sedaxane, silthiofam, simeconazole, spiroxamine,streptomycin, tebuconazole, tebufloquin, teclofthalam, tecnazene,terbinafine, tetraconazole, thiabendazole, thifluzamide, thiphanate,thiram, tiadinil, tolclosfos-methyl, folfenpyrid, tolprocarb,tolylfluanid, triadimefon, triadimenol, triazoxide, triclopyricarb,tricyclazole, tridemorph, trifloxystrobin, triflumizole, triforine,validamycin, and vinclozolin.

A pesticide intended for use against plants is known as an herbicide asdescribed above.

A pesticide intended for use against insects is known as an insecticide.Examples of insecticides are: organochlorides such as Aldrin, chlordane,chlordecone, DDT, dieldrin, endofulfan, endrin, heptachlor,hexachlorobenzene, lindane, methoxychlor, mirex, pentachlorophenol, andTDE; organophosphates such as acephate, azinphos-methyl, bensulide,chlorethoxyfos, chlorpyrifos, diazinon, chlorvos, dicrotophos,dimethoate, disulfoton, ethoprop, fenamiphos, fenitrothion, fenthion,malathion, methamdophos, methidathion, mevinphos, monocrotophos, naled,omethoate, oxydemeton-methyl, parathion, phorate, phosalone, phosmet,phostebupirim, phoxim, pirimiphos-methyl, profenofos, terbufos, andtrichlorfon; carbamates such as aldicarb, bendiocarb, carbofuran,carbaryl, dioxacarb, fenobucarb, fenoxycarb, isoprocarb, methomyl;pyrethroids such as allethrin, bifenthrin, cyhalothrin, cypermethrin,cyfluthrin, deltamethrin, etofenprox, fenvalerate, permethrin,phenothrin, prallethrin, resmethrin, tetramethrin, tralomethrin, andtransfluthrin; neonicotinoids such as acetamiprid, clothiandin,imidacloprid, nithiazine, thiacloprid, and thiamethoxam; ryanoids suchas chlorantraniliprole, cyanthaniliprole, and flubendiamide.

A pesticide intended for use against mites is known as a miticide.Examples of miticides are permethrin, ivermectin, carbamate insecticidesas described above, organophosphate insecticides as described above,dicofol, abamectin, chlorfenapyr, cypermethrin, etoxazole, hexythiazox,imidacloprid, propargite, and spirotetramat.

A pesticide intended for use against snails and other mollusks is knownas a molluscicide. Examples of molluscicides are metaldehyde andmethiocarb.

A pesticide intended for use against rodents is known as a rodenticide.Examples of rodenticides are warfarin, coumatetralyl, difenacoum,brodifacoum, flocoumafen, bromadiolone, diphacinone, chlorophacinone,pindone, difethialone, cholecalciferol, ergocalciferol, ANTU,chloralose, crimidine, 1,3-difluoro-2-propanol, endrin, fluroacetamide,phosacetim, pyrinuron, scilliroside, strychnine,tetramethylenedisulfotetramine, bromethalin, 2,4-dinitrophenol, anduragan D2.

A pesticide intended for use against viruses is known as a virucide.Examples of virucides are cyanovirin-N, griffithsin, interferon,NVC-422, scytovirin, urumin, virkon, zonroz, and V-bind viricie.

A persistent organic pollutant is a toxic organic chemical thatadversely affects human and environmental health, can be transported bywind and water, and can persist for years, decades, or centuries owingto resistance to environmental degradation by natural chemical,biological, or photolytic processes. Persistent organic pollutants areregulated by the United Nations Environment Programme 2001 StockholmConvention on Persistent Organic Pollutants. Examples of persistentorganic pollutants are Aldrin, chlordane, dieldrin, endrin, heptachlor,hexachlorobenzene, mirex, toxaphene, polychlorinated biphenyl (PCBs),dichlorodiphenyltrichloroethane (DDT), dioxins, polychlorinateddibenzofurans, chlordecone, hexachlorocyclohexane (α- and β-),hexabromodiphenyl ether, lindane, pentachlorobenzene, tetrabromodiphenylether, perfluorooctanesulfonic acid, endosulfans, andhexabromocyclododecane.

In some embodiments, the nanocomposite sorbent may be free flowing orsupported on or within a substrate, for example, a column. Examples ofsupported nanocomposite sorbents include materials and geometries wherethe nanocomposite sorbent is supported within a fixed bed, a staticpacked bed, a fluidized bed, embedded in a porous support (such as aporous polymer matrix), in or on a ceramic support, in or on a polymersupport, or in or on a silica support. In preferred embodiments, thenanocomposite sorbent is employed in an amount of 0.2 to 20 mg/mL,preferably 0.5 to 15 mg/mL, preferably 1 to 11 mg/mL, preferably 5 to 10mg/mL of water to have organic pollutants removed.

In some embodiments, the method involves addition of powderednanocomposite sorbent to the water to have an organic pollutant beremoved to form a purification mixture. In some embodiments, thepurification mixture is shaken, stirred, agitated, or other method ofachieving temporary homogeneity of the purification mixture. Inpreferred embodiments, the purification mixture is shaken at 10 to 1000rpm, preferably 50 to 500 pm, preferably 125 to 250 rpm, preferably 150rpm.

In alternative embodiments, the contacting comprises delivering amixture into a feed side of a chamber comprising the nanocompositesorbent that divides the chamber into the feed side and a permeate side,such that at least a portion of the water permeates the nanocompositesorbent and recovering from the permeate side purified water depleted inthe organic pollutant compared to the water supplied to the feed side.The chamber used for the present method may be of any shape so long asthe nanocomposite sorbent can be securely housed and utilized inside thechamber to accomplish the removal of the organic pollutant. The chambermay also include an inlet configured to accept feed material, a firstoutlet configured to expel a permeate, and an optional second outletconfigured to expel a retentate. The chamber can be configured to bepressurized so as to push feed material though the inlet, permeatethrough the first outlet and optionally, retentate through the secondoutlet. The chamber can alternatively be configured to operate atreduced pressure as to pull feed material through the inlet, permeateout through the first outlet and optionally, retentate out through thesecond outlet. The chamber may also include a pump to provide a forcefor moving water from the feed side to the permeate side. In one or moreembodiments, a force is provided to deliver the water into contact withthe nanocomposite sorbent. The water may have a flow rate of 0.001 L/minto 1,000 L/min, 0.005 L/min to 500 L/min, 0.01 L/min to 100 L/min, 0.05L/min to 10 L/min, 0.1 L/min to 5 L/min, or 0.5 L/min to 2 L/min.Alternatively, the water may stay stagnant over the nanocompositesorbent or be stirred, shaken, or agitated as previously described.

In some embodiments, the water used in the method has a temperature of 1to 99° C., preferably 20 to 90° C., preferably 21 to 75° C., preferably25 to 50° C. In some embodiments, the water has a pH of 6. 5 to 14,preferably 6. 6 to 13, preferably 6.75 to 12, preferably 7 to 11. Inpreferred embodiments, the water and the nanocomposite sorbent are incontact for 5 to 120 minutes, preferably 15 to 105 minutes, preferably30 to 90 minutes.

In some embodiments, the contacting is performed by passing the waterthrough the nanocomposite sorbent. In some embodiments, thenanocomposite sorbent may be used in series with other currently knownadsorption materials to enhance the removal of an organic pollutant fromwater or to remove a different type of impurity from water that is notan organic pollutant.

In terms of the present disclosure, the adsorption interaction betweenthe organic pollutant and the nanocomposite sorbent may bechemisorption, physisorption, or mixtures thereof. In at least oneembodiment, organic pollutant is adsorbed onto the nanocomposite sorbentvia a physisorption process, meaning the process is primarily physicaland preferably no chemical changes occur on the nanocomposite sorbent ororganic pollutant.

In some embodiments, the water has an organic pollutant present in anamount of 0.01 to 1000 ppm, preferably 0.1 to 500 ppm, preferably 0.5 to400 ppm, preferably 1 to 250 ppm, preferably 10 to 200 ppm, preferably50 to 150 ppm. In some embodiments, the purified water has least 25%less organic pollutant than that present in the water before contactwith the nanocomposite sorbent, preferably at least 30% less, preferablyat least 40% less, preferably at least 50% less, preferably at least 60%less, preferably at least 70% less, preferably at least 80% less,preferably at least 90% less, preferably at least 95% less than thatpresent in the water before contact with the nanocomposite sorbent. In apreferred embodiment, the purified water is substantially free of theorganic pollutant, for example, the stream contains less than 10 ppm,preferably less than 1 ppm, preferably less than 100 ppb, preferablyless than 1 ppb, preferably less than 0.1 ppb, preferably less than 1ppt of the organic pollutant. In a most preferred embodiment, thepurified water is devoid of the organic pollutant.

In one or more embodiments, the method of the present disclosure furtherinvolves eluting the organic pollutant from the nanocomposite sorbent,and reusing the nanocomposite sorbent. The eluting can be performed asdescribed above. The nanocomposite sorbent of the present disclosure maybe regenerated (i.e. eluted) and reused up to 3 cycles with a loss of nogreater than 10 percent, preferably no greater than 9 percent,preferably no greater than 8 percent, preferably no greater than 7percent, preferably no greater than 6 percent, preferably no greaterthan 5 percent, preferably no greater than 4 percent, preferably nogreater than 3 percent, preferably no greater than 2 percent, preferablyno greater than 1 percent in the organic pollutant uptake capacity,preferably up to 15 cycles, preferably up to 25 cycles, preferably up to50 cycles, preferably up to 100 cycles, preferably up to 150 cycles,preferably up to 200 cycles, preferably up to 250 cycles, preferably upto 300 cycles, preferably up to 350 cycles, preferably up to 400 cycles,preferably up to 500 cycles, preferably up to 625 cycles, preferably upto 750 cycles, preferably up to 1,000 cycles.

The examples below are intended to further illustrate protocols forpreparing and characterizing the nanocomposite sorbent discussed aboveand for assessing the organic pollutant adsorption properties of saidnanocomposite sorbent and are not intended to limit the scope of theclaims.

Where a numerical limit or range is stated herein, the endpoints areincluded. Also, all values and subranges within a numerical limit orrange are specifically included as if explicitly written out.

As used herein the words “a” and “an” and the like carry the meaning of“one or more.”

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that, within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

All patents and other references mentioned above are incorporated infull herein by this reference, the same as if set forth at length.

EXAMPLES Reagents and Equipment

The potassium persulfate, acrylic acid and acrylamide reagents used inthe synthesis of the CNT-AaAm adsorbent were bought from Sigma AldrichCompany. 1000 mg/L stock solution of phenol (Merck Company, Darmstadt,Germany) was prepared in deionized distilled water. The solutions withdifferent concentrations in mg/L were prepared by diluting of the stocksolution using distilled water.

The method of Chemical Vapor Deposition (CVD) was used for the purposeof growing carbon nanotubes [S. Iijima, Nature, 354, (1991) 56; R.Saito, G. Dresselhaus and M. S. Dresselhaus, Imperial College Press,(1998); A. Loiseau, P. Launois, P. Petit, S. Roche and J.-P. Salvetat,Springer, (2006); and A. J. Hart and A. H. Slocum, Journal of PhysicalChemistry B, 110, (2006) 8250-8257]. The machine utilized in order togrow the CNTs contains following separate elements from vendorAbsoluteNano as shown in FIG. 1 : heating substrate (101), gasproportioner (102), gases (103), controller (104), preheater (105),furnace heater controller (106), and a SabreTube Desktop ThermalProcessing System furnace (107).

The SabreTube furnace used in the growth of CNT is subjected to work inlow-pressure conditions where the pressure is below the atmosphericpressure. The pressure is made to not cross more than 0.3 psi (2.0 KPa)over the atmospheric pressure. In the apparatus, a 0.5 mm thicknessdoped silicon bar is the main component of the heating element in thefurnace. This silicon bar consisting element is mounted in the apparatusinside a tube made of quartz, which has both ends of the tube sealedclosed. In this tube, the complete reaction and internal processes canbe observed directly in a visual manner. In order to track thetemperature changes of the heating element, an IR sensor is used, whichis kept mounted below the quartz tube. The output of the IR sensor iskept equivalent to a thermocouple of Type K (40 mV at 800° C. ).

In this method, in order to control the furnace, a control box is usedthat integrates IR sensor and power supply. A heating circuit is usedthat maintains the voltage used on the element below 50 volts and amaximum current of 15 Amps. Moreover, the output of the infrared sensoris typically mounted on the backside of the furnace and is integratedusing a type K thermocouple jack, which is a commonly found size of thepanel. In order to increase the gas temperature to 1020° C., they arepassed through the pre-heating chamber. The pre-heating chamber ismaintained at this temperature and enhances the reaction rate of theincoming gases. In this manner, the pre-heating process essentiallyincreases the growth of CNT growth. Three different gases areused—Ethylene (99.5%), Hydrogen (99.999%), and Helium (99.999%) In thisprocess, Helium has the purpose of displacement of the atmospheric airin the apparatus. Hydrogen is used in the pre-growth stage of theprocess to flow alongside the catalytic layer of Iron and aluminum oxidewhile subjected to high temperature. Ethylene is as a source gas tointroduce hydrocarbons. In order to fluctuate and control the flow rateof individual gases, a gas proportioner apparatus is used. To produceCNTs, during the process of thermal CVD, a catalytic layer is used,which is aluminum oxide having a coating of Iron. However, before theaddition of this aluminum oxide and Iron as a catalytic layer, a 100 nmthickness layer of silicon dioxide is developed on a silicon wafer. Onthe silicon dioxide layer, a layer of catalytic Iron and Aluminum oxideis evaporated using e-beam evaporator of Model Temescal FC2000 frome-beam FP and Atomic Layer Deposition (ALD). The iron oxide layer isformed due to air exposure and it then converts back to Fe and leads tothe growth of catalytic Nano-particles when high temperature andhydrogen is subjected in the process.

Synthesis of Carbon Nanotubes

In order to grow highest quality CNTs; optimum conditions are used interms of thickness of the catalytic, metal used as catalytic,temperature of the substrate, precise timing of introducing gas in thechamber, rate of flowing the gases, and specific gas types used. Thefabrication process starts with 8×8 mm silicon wafer, on the top 100 nmof SiO₂ is deposited via sputtering and annealed in air at 450° C. for 2hours. 10 nm of Al₂O₃ is deposited is deposited via atomic layerdeposition (ALD) at 220° C. and annealed at 350° C. for 1 hour. Finally,a thin layer of Fe (1 nm) is evaporated onto the surface using e-beamevaporator of Model Temescal FC2000.

The entire procedure of growing CNTs begins with initial check to seethat all of the valves are properly closed and that the furnace is notreceiving power through controller before the sliding door is openedmanually as shown in FIG. 1 . After opening the sliding door, safetyshield is removed from the furnace. Afterwards, a careful displacementof the quartz tube in the right side gives path to the chamber. The two8×8 mm silicon device is placed in the chamber facing in up direction.After that, a silicon cap is then used to cover the downstream side ofthe substrate for observational purpose. It is also to be ensured thatthe cap's non-polished end should be in direct contact with thecatalytic layer. Keeping all the power controller in off condition,helium gas is introduced through the valve (to achieve output reading of50 psi) and on the gas proportioner, the helium gas should have 1,000sccm and temperature is raised to 1020° C. after three minutes inpre-heater.

At a constant flow, helium is passed through the pre-heater ontemperature of 1020° C. After 5-10 minutes, hydrogen is released at 250sccm controlled by the valve and helium is also reduced to 140 sccm fora period of two minutes. Furnace controller is turned on to reach 820°C. temperature and after that, temperature of the silicon substrate isstabilized in 30 seconds. In order to grow the CNTs, the flow ofEthylene is maintained at 120 sccm. At this stage, growth of CNT startsafter waiting for 30 minutes. Valves for ethylene and hydrogen isclosed, and both the preheater and furnace controller are turned off.Moreover, flow of helium is increased to 1,000 sccm and kept this wayfor five minutes of duration. In order to cool the system, helium flowis reduced to 120 sccm from 10 to 10 minutes. FIG. 2A and 2B show highresolution SEM image captured using TESCAN VEGA3 for the synthesizedCNTs with the length of 85.85 μm at 30° C.

Synthesis of CNT-AaAm

For the synthesis of CNT-AaAm, CNTs were dispersed in deionized water in500 ml round-bottom flask. The flask was left in the sonicator untilparticles were well dispersed. Then, around 5 g of acrylamide was addedto the dispersed CNTs under agitation. After well mixing, 5 g of acrylicacid was added to the dispersed mixture under stirring conditions. Thecomponents were then heated at 50° C. Potassium persulfate was added tothe mixture to initiate the polymerization. The obtained material waskept under stirring conditions until reaction completed. The obtainedproduct was washed with deionized water several times, until thewashings became clear, then filtered and dried in an air-dried oven at80° C. for 2 days. Then, they were crushed and sieved to get uniformparticle sizes. FIG. 3 shows the proposed structure of the preparedCNT-AaAm.

Batch Adsorption Procedure

The adsorbent was added to the phenol solution into a centrifuge tubeand shaken at 150 rpm onto a shaker (Lab Line Instrument) to achieveequilibrium at different temperatures, 25, 50 and 75° C. After that, thesupernatant phase separated from the mixture was analyzed at 510 nmwavelength using a UV-visible spectrophotometer (Perkin-Elmer Lambda 35model, USA). To perform the kinetic studies, the adsorption runs wererepeated at different intervals until reaching the equilibrium time. Thebatch experiments also were also taken place at various pH valueschanged from 2 to 8 using 0.1 M solution of HCl or NaOH. The each batchrun was replicated three times to make sure the precision of themeasured data.

The phenol adsorption (%) was calculated using following equation:

${{Adsorption}(\%)} = {\frac{C_{f} - C_{i}}{C_{i}} \times 100}$

where C_(i) (mg/L) and C_(f) (mg/L) are the initial and final phenolconcentrations, respectively. In order to evaluate the recyclingperformance of the adsorbent, the adsorption and desorption processeswere repeated subsequently for seven times. The phenol adsorbed on theCNT-AaAm was desorbed using methanol. After each cycling theUV-measurement was conducted in triplicate.

The crystalline structure of the product was identified by X-raydiffraction (XRD) (Shimadzu XRD-7000, with monochromatic high-intensityCu Kα radiation (λ=1.5406 Å)) with 2 θ=10-90° and by a scan rate of0.5°/min. The morphology, distribution and shape of the samples wereobtained directly by Transmission Electron Microscopy (TEM) (Morgagni268) and Scanning Electron Microscope (SEM) (Inspect S50). The samplewas prepared for TEM analysis by dispersing in alcohol and shaking in anultrasonic for 10 min. A suspended drop then was dried on thecarbon-coated copper grid at room temperature.

Characterization of the Prepared CNTs XRD Analysis

FIG. 4 shows the XRD pattern of the main features of Carbon NanotubesCNTs. The XRD studies of powder fabricated by Chemical Vapor Deposition(CVD) can be indexed the crystalline nature of CNTs (JCPDS number96-101-1061) [Soleimani H, Baig M K, Yahya N, Khodapanah L, Sabet M,Demiral B M R, et al. Results Phys., 1, 9, (2018) 39-48]. The two strongdiffraction peaks appear at 2 θ=26.3° and 43.3° correspond to (002) and(100), respectively, and confirm it is highly crystalline [Saleh T A,Gondal M A, Drmosh Q A, Yamani Z H, AL-yamani A., Chem Eng J., 166, 1,(2011) 407-12 and Lafuente E, Callejas M A, Sainz R, Benito A M, Maser WK, Sanjuán M L, et al., Carbon, 46, 14, (2008) 1909-17]. The highcrystallinity endows the material with high strength and modulus. Thesharpness of the (002) peak indexes to the reflection of the hexagonalgraphite structure of CNTs and is used to measure the crystal size ofCNTs. The average crystal size (D) can be measured by Scherrer equation:

$D = \frac{k\lambda}{\beta\cos\theta}$

Where λ is the wavelength (1.5406 Å), β is the full width at halfmaximum (FWHM), θ is the diffraction angle, and k is the Schererconstant (0.91). Bragg's law derives to the Scherrer formula and it islimited to nanoscale particles only. The increase in the degree ofcrystallinity in the carbon materials makes XRD peaks more sharp. Theparameters of CNTs are summarized in Table 1.

TABLE 1 d-spacing and crystallite size D of CNTs. 2θ° d-spacing [Å] (h kl) FWHM D (nm) 26.2289 3.39493 (0 0 2) 1.40000 6.09

Morphological Analysis

FIG. 2A and 2B illustrate the morphology of the CNTs. The bundles ofcarbon nanotubes appear clearly in the TEM image as shown in FIG. 2A.CNTs exhibit a straight morphology and the existence of the wall withhigh crystallinity. Additionally, CNT morphology was examined by SEM.FIG. 2B displays a SEM image of the CNTs. It shows soft surfaces andstraight structures of the CNTs, this confirms that the carbon nanotubeswere grown with good defined morphology.

The IR spectrum, FIG. 5 , of CNTs indicates bands at wavenumbers 3444cm⁻¹, which can be attributed to the stretching vibrations of isolatedsurface —OH moieties and —OH in carboxyl groups. The bands in the1750-1550 cm⁻¹ range are attributed to C═C in aromatic rings and to C═Ogroups such as carboxylic acid, ketone/quinone. The bands at around 1310to 940 cm⁻¹ indicate the presence of the bond of C—O in differentchemical environment. The band at around 1550 cm⁻¹ is attributed toaromatic and unsaturated structure of C′C bonds. The band at around 1415cm⁻¹ could be due to OH in-plane deformation and C—O [L. Stobinski, B.Lesiak, L. Kövér, J. Tóth, S. Biniak, G. Trykowski, J. Judek, Journal ofAlloys and Compounds, 501, 1, (2010) 77-84].

Characterization of the Prepared CNT/AaAm

The IR spectrum, FIG. 5 , of CNT/AaAm indicates bands observed at therange of 3100-3500 cm⁻¹ is N—H stretching band of amine groupsoverlapped with the broad band in the range of 3400 cm⁻¹ of O—H. Theweak peaks at 2900 cm⁻¹ are C—H stretching bands. The peak at 1581 cm⁻¹is due to C═C stretching band. The C═O group connected to the carboxylgroup gives an absorption peak at 1736 cm⁻¹ [Oldani M. & Schock G., J.Memb. Sci., 43, (1989) 243-258]. The C═O group connected to the amidegroup gives absorption peak at 1679 cm⁻¹ in aliphatic C—N stretchingband is observed 1159-1173 cm⁻¹ [Smith B. C., CRC Press, 1998 and TangC., Kwon Y. & Leckie J., J. Memb. Sci., 287, (2007) 146-156]. The SEMimages of CNT/AaAm are shown in FIG. 6A and 6B, which reveals the coarsesurface of CNT/AaAm. The images indicate a surface where some polymerchains and nanotubes emerge from a continuous surface. The EDX spectrum,FIG. 7 , indicates the CNT/AaAm consists of carbon, oxygen, andnitrogen. It should be mentioned that although hydrogen is part of thestructure, it is usually not detected by the SEM/EDX equipment.

Adsorption Efficiency

The prepared CNT/AaAm was evaluated for its efficiency for the removalof phenol from waters. In order to optimize the experimental parametersand get insights into the best experimental conditions, design ofexperiments (95% confidence limit) was established to get insights onthe interactions between the experimental conditions that affect thesorption. Experimental conditions or factors that were optimized hereinclude pH, adsorbent dosage, contact time and the initialconcentration. −1, 0, 1 were used to represent the low, mid and highlevels for the parameters with the generated data are shown in Table 2and Table 3. The experimental; tests were performed and the response wasinserted for analysis.

TABLE 2 Design matrix of the factorial design (DOE). Variable Low(−)Central point (0) High(+) pH 3 7 11 Adsorbent dosage 10 500 200 (D) (mg)Contact time (T) 5 30 90 (min) Initial concentration 5 10 50 (C) (ppm)

TABLE 3 Experimental set Experiment pH Dosage Time ConcentrationRecovery (%) 1 −1 −1 −1 −1 15 2 1 −1 −1 −1 25 3 −1 1 −1 −1 30 4 1 1 −1−1 36 5 −1 −1 1 −1 42 6 1 −1 1 −1 63 7 −1 1 1 −1 75 8 1 1 1 −1 100 9 −1−1 −1 1 50 10 1 −1 −1 1 55 11 −1 1 −1 1 45 12 1 1 −1 1 60 13 −1 −1 1 130 14 1 −1 1 1 55 15 −1 1 1 1 95 16 1 1 1 1 100 17 0 0 0 0 97 18 0 0 0 097 19 0 0 0 0 96 20 0 0 0 0 95 21 0 0 0 0 97

The normal plot of the standardized effects was conducted to verify thenormality of the data, FIG. 8A-8C. The significance level for this modelwas chosen to be 0.05 (95% confidence level). A reference line is drawnto indicate that the factors which extend past this line are potentiallyimportant. The effects that are above the reference line arestatistically significant at 95% confidence level. Contact time and thedosage are the highest two factors affecting more the adsorption. Amongthe interactions between the factors, the interaction between the dosageand the contact time was significantly affecting the process. Maineffect and Pareto plots indicate also the parameters affecting more theadsorption. FIG. 9 depicts the interaction plots for the response ofdata means for the adsorption of phenol over CNT-AaAm. The magnitude ofeffects of each factor and their interactions found to increase in thefollowing order dosage and contact time>initial concentration andcontact time>contact time and pH. The decrease in the solution pH to 3.0 decreased the % removal of the phenol while the adsorption was higherat higher pH.

Recycling Performance of the Synthesized CNT-AaAm

The disposal of the used adsorbent can cause considerable environmentaltrouble because of the great quantity of discharged toxic pollutant. Itis a clear fact that the reimburse obligation for new adsorbents afterevery adsorption process is non-economical. Therefore, to study therecycling prospective of the used adsorbent, a renewal process thatincluded the following adsorption/desorption cycles was conducted forthe synthesized CNT-AaAm sorbent. FIG. 10 indicates regeneration yieldsof the developed sorbent during the seven cycles. As seen from theresults, the adsorption and desorption yields were still over 95% up tothe first five cycles. After that, the adsorption efficiency wasslightly reduced to 91%. This indicates that the prepared CNT-AaAm hasreasonable recycling performance for the phenol removal from aqueoussolutions.

Proposed Mechanisms of Interactions

There are several possible phenol-adsorbent interaction mechanismsinvolving π-π interaction between the bulk π system on the materialsurfaces and phenol rings. It includes also hydrogen bonds because ofthe polymer chain grafted on CNTs), and electrostatic interactions dueto the charged CNT surface. In addition, the outer surface of thenanotubes provide distributed hydrophobic sites for organic pollutants,however, hydrophobic interactions may not completely explain theinteractions between phenol and CNTs. Thus, various adsorptionmechanisms respond differently to the change in environmentalconditions. Based on this, there could be multiple mechanisms actingsimultaneously. The removal of phenol may comprise the interactionsillustrated in FIG. 11 .

1-6. (canceled)
 7. The water purification method of claim 14, whereinthe nanocomposite sorbent comprises 70 to 80 wt % carbon, 5 to 10 wt %nitrogen, and 10 to 25 wt % oxygen, based on a total weight ofnon-hydrogen elements of the nanocomposite sorbent. 8-13. (canceled) 14.A water purification method, comprising: removing a phenol from pollutedwater by: contacting the polluted water containing the phenol with ananocomposite sorbent to form a purification mixture, and separating thenanocomposite sorbent from the purification mixture to form purifiedwater, wherein the nanocomposite sorbent comprises: a carbonnanotube-grafted acrylic acid/acrylamide copolymer composite, whereinthe carbon nanotube-grafted acrylic acid/acrylamide copolymer compositecomprises 37.5 to 62.5 wt % of poly(acrylic acid), 0.01 to 2 wt % ofcarbon nanotubes, and the remaining wt % of polyacrylamide, based on atotal weight of the carbon nanotube-grafted acrylic acid/acrylamidecopolymer composite, wherein a weight ratio of poly(acrvlic acid) topolvacrylamide in the carbon nanotube-grafted acrylic acid/acrylamidecopolymer composite is 0.75:1 to 1.25:1, wherein the carbon nanotubesare covalently bonded to the acrylic acid/acrylamide copolymer compositethrough a carbon-carbon bond, and wherein the carbon nanotubes have nofunctionalization other than the covalent bond to the acrylicacid/acrylamide copolymer; and wherein the carbon nanotubes have alength of 50 to 125 μm and an average diameter of 5 to 7 nm, theneluting the phenol from the nanocomposite sorbent by washing with atleast one wash solvent selected from the group consisting of methanolethanol, propanol. and butanol.
 15. The water purification method ofclaim 14, wherein the nanocomposite sorbent is employed in an amount of0.2 to 20 mg per mL of the water.
 16. (canceled)
 17. The waterpurification method of claim 14, wherein the polluted water has a pH of6.5 to 14 and the nanocomposite sorbent is contacted with the pollutedwater for 5 to 120 minutes.
 18. (canceled)
 19. The water purificationmethod of claim 14, wherein the nanocomposite sorbent has a reversiblephenol adsorption capacity of 5 to 2500 μg of phenol per mg ofnanocomposite sorbent.
 20. The water purification method of claim 19,wherein the nanocomposite sorbent retains 90 to 100% of the reversiblephenol adsorption capacity after 6 cycles of adsorption-elution.
 21. Thewater purification method of claim 14, wherein the nanocomposite sorbentis supported on a fixed bed during the contacting.
 22. The waterpurification method of claim 14, wherein during the contacting thenanocomposite sorbent is contained within a chamber having a feed sideand a permeate side and the polluted water is fed into the chamberthrough the feed side to pass through the nanocomposite sorbent and exitas the purified water through the permeate side.